I am using an Arduino UNO R3 with a 4 wheeled robot in my project. I have searched several robotics vendors sites for a limit switches to use as bump sensors. I am not having much luck narrowing down my search though as I have never used these sensors before. I will need to purchase dozens of these parts as it is for a course I am teaching. As a result cost is a factor. I would like to keep the price of each unit below $1.50.
Can anyone recommend (or not recommend) any specific products which they may have experience with?
Actually I am. How do you imagine teachers become qualified? Do you think there are lots of people who go to school to get an electrical engineering degree and then suddenly decide to start teaching electronics at the secondary level? Most of what we learn is self-taught and that is my process right now. I guess I'm done asking questions on this forum.
sparkfun.com has some limit switches (called bumpers I think - found them in a robot kit) - yes $5.- but that is a fancy little board - but a couple of bolts and pieces of wire - sort of a DIY thing if you wanted the students to build their own (if you make them your time would be worth more) - I would expect that Parallax (they use a different processor but a strong support teachers thing) would have a similar switch / bumper
You might also try another post to the effect "Instructor new to Arduino & robots" and ask for help for links to instructor materials - I would be surprised if there are not some teachers here
One problem that leads to short answers are the people that show up with not much experience and have slept through their class and expect the forum members to design their Senior Project for them complete with 400 lines of code in two days for their due date - they tend to draw short rude answers - so best to keep your questions not looking like one of your dozy students
Good luck with your class, as someone that teaches other classes the first time developing (or following) a new class can be a bit rough - even if the presentation was all done for you
This article sheds some light on why a switch's AC and DC ratings differ.
The ebay ad for the switches mentioned is silent on the dc rating, and so too (judging from the photos) are the switches themselves, so how does one know what's safe in that case?
What would happen if there was a fire and the insurers said "so what was the switch's dc rating?" and the switch wasn't marked for dc?
Thanks for the article on switches when I used to work in industrial plants we always payed close attention to the switch ratings and the use, environment (dust, water gas, etc) - a few times I saw the wrong switch used and all types of problems - but at 5 VDC things are simpler than 440 VAC and 600 hp electric motors
Thank you to all who have provided a great deal of information in these recent posts. I think I can move forward on this now. The idea of having the students go a little deeper into the project by trying to build these seems interesting as well.
I have ordered a few different options so I can test them out myself. I did try to figure this out myself first but I have no formal training at all in electronics so I would rather defer to the expertise here if I am unsure. I regularly post answers on a stack exchange subforum where I can actually provide some help. In those posts I try to always assume positive intentions and respond as almost all of you have to this question. This is exactly the same attitude I take with my students.
Thanks again for the advice. If I have other questions on this topic which I cannot answer myself I will ask.